The present invention relates to umbrellas and particularly, but not exclusively, to umbrellas the opening and closing of which is motorised.
A typical umbrella is constructed with a support pole carrying at its uppermost end a crown with radiating ribs pivotally connected thereto and a sleeve sliding over the pole with struts being interconnected between the sleeve and the ribs. Various motorised drive mechanisms have been provided to slide the sleeve along the pole in order to cause the struts to splay the ribs attached to the crown upwardly and outwardly.
U.S. Pat. No. 6,543,464 describes an umbrella where the linear movement of the sleeve along the pole is driven by a threaded rod received within a tubular support pole and cooperating with a threaded nut to which the sleeve is fixed. A drawback with this design is the necessity to provide longitudinal openings in the pole for receiving fasteners connecting the internal nut to the external sleeve. Such openings not only detract from the appearance of the umbrella but also permit the entry of foreign matter which is likely to degrade the performance and reduce the working life of the threaded rod and nut.
U.S. Pat. No. 4,424,824 teaches an umbrella having a shaft telescopically received in the support pole and to the outer end of which the crown is fixed such that by retracting the shaft the ribs are splayed outwardly. The flexible member connecting the shaft and sleeve, as well as the cooperating pulley necessary in this umbrella, add considerable complexity and cost to this umbrella. Furthermore, particularly when the umbrella is placed in storage when not in use, it is disadvantageous that the overall length of the umbrella is extended when it is closed.
It is an object of the present invention to overcome or substantially ameliorate at least one of the above disadvantages and/or more generally to provide an improved umbrella.